If it is centralised and it has no publicly available blockchain then there is no reason to discuss it in the light of the cryptocurrency: there is no difference with e-gold or paypal of visa or mastercard: you just know that some server has a db that contains a record with your available balance.
The most important motivation for Satoshi (or last drop that pushed him, I do not know precisely, but he mentioned exactly that event in his whitepaper) to develop the blockchain technology was a egold collapse caused by feds: they just shut it down. Any centralised solution may be shut down.
This is true. The only similarity our concept shares with cryptocurrency is our need to use a kind of digital currency. I believe the most important question needing answer is how we intend to come about this digital currency. We have no blockchain so we can't "mine" coins and trying to mimicking this process seems like we are trying hard to be similar to cryptocurrency. Thanks